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I've had COVID, am I protected? Do I still have to respect physical distance, wash my hands, wear the mask...?

Text updated on 2021-06-19

It is not known how many months one is immune after a first infection with the coronavirus SARS-CoV-2. Some cases of re-infection have been observed. Even if re-infections are rare, one must remain vigilant and continue to apply barrier measures and wear a mask in enclosed spaces.

Yes, you are protected but the duration of protection is unknown at this time. The duration of protection varies according to the viral infections. For cold coronaviruses, immunity is around 30 months. For the measles virus, which is not a coronavirus, immunity lasts for life.

In the case of the coronavirus SARS-CoV-2, it is still too early to know the duration of protection. In retrospect, it is estimated that the duration of protection is at least 11 to 13 months.

After an infection with COVID-19infection, it is possible to find out if you are immune by doing a serological test. See the question What are the tests to find out if I have already had COVID-19 ?

There are some known cases of re-infection with the coronavirus, some with more severe symptoms the second time around and some without symptoms the second time around. See the question Can you catch COVID twice?. If one is re-infected by the SARS-CoV-2, that one has an asymptomatic form and that one does not respect the barrier gestures nor the wearing of the mask, one risks transmitting the coronavirus and infecting other people without knowing it. It is therefore important to remain vigilant and to continue to respect the barrier measures, to wash your hands frequently and to wear a mask in enclosed spaces, even if this is restrictive.

Furthermore, our hands can be a vector of transmission without us being infected. If we touch a coronavirus-contaminated SARS-CoV-2surface, we can carry it to another surface. So you can infect other people without being infected with the coronavirus yourself.

Finally, hand washing protects against many other viruses and bacteria. Therefore, you should continue to wash your hands to prevent the transmission of COVID-19, just like other infections!

Sources

Analysis of serological and clinical data accumulated in the Netherlands in ten men (aged 27-40 years at the start of the study) for 35 years, from 1985 to 2020, who volunteered to have blood samples taken approximately every 3-6 months. A total of 132 common cold coronavirus (HCoV: NL63, 229E, OC43 and HKU1) infections were detected, i.e. between 3 and 22 infections per individual. A similar median reinfection time of approximately 30 months was measured for each of the 4 cold coronaviruses. In some cases, re-infection with the same coronavirus occurred 6 months after the first one. For each coronavirus, there are half as many infections from May to September as from December to March.

Edridge, A. W., Kaczorowska, J. M., Hoste, A. C., Bakker, M., Klein, M., Jebbink, M. F., .... & Sastre, P. (2020). Coronavirus protective immunity is short-lasting. MedRxiv.

Immunity to the measles virus lasts a lifetime.

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Study reporting the case of a patient who tested positive for the SARS-CoV-2 coronavirus on his return from Spain, at the Hong Kong airport, four and a half months after a first infection. The differences between the viral RNA sequences collected during the two infectious episodes confirm that these are two successive independent infections.

To, K. K. W., Hung, I. F. N., Ip, J. D., Chu, A. W. H., Chan, W. M., Tam, A. R., ... & Lee, L. L. Y. (2020). COVID-19 re-infection by a phylogenetically distinct SARS-coronavirus-2 strain confirmed by whole genome sequencing. Clinical Infectious Diseases.

In this preprint, the authors report the case of a 25-year-old patient from Reno, Nevada, who developed a severe form of COVID-19 (with hospitalization and need for continuous oxygen supply) one month after the end of symptoms associated with a first infection that did not require hospitalization. Differences in viral RNA sequences between the two infectious episodes confirm that this is a reinfection and not a resurgence of the first infection.

Tillett, R., Sevinsky, J., Hartley, P., Kerwin, H., Crawford, N., Gorzalski, A., ... & Farrell, M. (2020). Genomic Evidence for a Case of Reinfection with SARS-CoV-2. Available at SSRN 3680955.

Measurement of the stability of the virus under different environmental conditions.

Chin, A., Chu, J., Perera, M., Hui, K., Yen, H. L., Chan, M., ... & Poon, L. (2020). Stability of SARS-CoV-2 in different environmental conditions. The Lancet Microbe.

Several people in the same family have been infected by asymptomatic individuals.

Ye, F., Xu, S., Rong, Z., Xu, R., Liu, X., Deng, P., ... & Xu, X. (2020). Delivery of infection from asymptomatic carriers of COVID-19 in a familial cluster. International Journal of Infectious Diseases.

Antibody persistence in the MERS disease 34 months after infection in 6 of 7 patients tested.

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Study in 176 patients infected with the SARS-CoV-1 virus which shows that the average duration of immunity against this disease is 24 months.

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In this longitudinal study, a cohort of 12,541 health care workers was followed for 31 weeks. The presence of anti-spike antibodies (to the coronavirus Spike protein) was associated with a reduced risk of infection with SARS-CoV-2. In these individuals with anti-spike antibodies, no symptomatic infections and only two cases of asymptomatic forms were observed. This suggests that prior infection with SARS-CoV-2 resulting in antibody production is associated with protection from reinfection for most individuals for at least 6 months.

Lumley, S. F., O'Donnell, D., Stoesser, N. E., Matthews, P. C., Howarth, A., Hatch, S. B., ... & Eyre, D. W. (2021). Antibody status and incidence of SARS-CoV-2 infection in health care workers. New England Journal of Medicine, 384(6), 533-540.

In this longitudinal study, 188 individuals with COVID-19 were recruited with predominantly asymptomatic forms (2% asymptomatic). Five to 8 months after their infection with SARS-CoV-2, anti-spike antibodies (against the Spike protein of the coronavirus) and anti-RBD antibodies (against the Receptor Binding Domain, a domain that binds to human cells) were detected in about 95% of the individuals. These results indicate that sustained immunity to secondary infection with COVID-19 infection is possible in most individuals.

Dan, J. M., Mateus, J., Kato, Y., Hastie, K. M., Yu, E. D., Faliti, C. E., ... & Crotty, S. (2021). Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection. Science.

This study shows that after being infected with SARS-CoV-2, the immune response is still present 13 months after infection. The risk of infection in people who have already had COVID-19 is reduced by 96.7% compared to those who have never had COVID-19.

Gallais, F., Gantner, P., Bruel, T., Velay, A., Planas, D., Wendling, M. J., ... & Fafi-Kremer, S. (2021). Anti-SARS-CoV-2 Antibodies Persist for up to 13 Months and Reduce Risk of Reinfection. medRxiv.